Monolithic structures having improved flaw tolerance

Details Monolithic structures having improved flaw tolerance Monolithic structures having improved flaw tolerance

F - Mech Eng,Light,Heat,Weapons

16

S

F16S 3/00 (2006.01) B64C 27/32 (2006.01)

Patent

CA 2256340

A monolithic structural member (10) operative for reacting steady and vibratory bending moment loads M about an applied loads axis X and having a specially configured cross-sectional configuration for providing improved flaw tolerance. The cross-sectional configuration (10) includes a central connecting element (18) and at least one pair of structural ribs (14a, 14b) being integrally formed with the central connecting element (18) and projecting outwardly thereof. The structural ribs (14a, 14b) are furthermore disposed in the tensile field produced by the steady portion of the bending moment loads M and are proximal to the centroid CT of the cross section (10). The cross-sectional configuration (10) defined by the structural ribs and connecting element produces a partial inertia ratio IX/IY greater than or equal to 1.0, which partial inertia ratio IX/IY has the advantageous effect of retarding or arresting crack propagation in the structural member (10). The cross-sectional configuration (10), as adapted for use in a helicopter rotor hub assembly (50), provides improved flaw tolerance and improved clearance between rotor hub assembly components. Specifically, the cross-sectional configuration (10) has a double-tee cross-sectional shape and is employed in areas corresponding to the midsection (64m) of each rotor assembly yoke (64) and shear segments (62) of the hub retention member (52). The double-tee cross- sectional configuration (10) facilitates higher flapwise and edgewise angular excursions between the yoke (64) and hub retention member (52) thus providing greater design flexibility and/or reducing the size and weight of the rotor hub assembly (50).

L'invention concerne un élément structural monolithique (10) conçu pour réagir aux charges M de moments de flexion vibratoires et constants sur un axe X de charges appliquées et présentant une section spécialement conçue pour permettre une tolérance de défauts accrue. Ladite section (10) comporte un élément central de liaison (18) et au moins une paire de nervures structurales (14a, 14b) formant partie intégrante de l'élément central de liaison (18) et saillant vers l'extérieur de ce dernier. Les nervures structurales (14a, 14b) sont, de plus, placées dans le champ de traction produit par la partie constante des charges de moments de flexion M et sont proximaux par rapport au centre de gravité C¿T? de la section (10). La section (10) définie par les nervures structurales et l'élément de liaison produit un rapport d'inertie partielle l¿x?/l¿y? supérieur ou égal 0 1,0, lequel rapport a pour effet avantageux de retarder ou de stopper la propagation des fissures dans l'élément structural (10). La configuration de la section (10), lorsqu'elle est destinée à un ensemble moyeu de rotor (50) d'hélicoptère, permet d'augmenter la tolérance de défauts et la garde entre les composants de l'ensemble moyeu de rotor. Spécifiquement, la section (10) a une forme de double té et est utilisée dans des zones correspondant à la section médiane (64m) de chaque étrier (64) d'ensemble rotor et aux segments de cisaillement (62) de l'élément de retenue (52) du moyeu. La section en double té (10) facilite les excursions hautes dans le sens du battement et de la traînée entre l'étrier (64) et l'élément de retenue du moyeu (52), ce qui permet une grande souplesse de conception et ou la réduction de la taille et du poids de l'ensemble moyeu de rotor (50).

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